This invention relates to surface illuminators, and more particularly to an improved such illuminator which employs LED light sources that are arrayed in a novel manner. More particularly this invention relates to an improved LED surface illuminator employing novel Fresnel-like diffuser elements which provide illumination at higher angles of incidence than was previously possible with known, prior art illuminators.
It has been customary in many, known illuminators to employ light emitting diodes (LED's) for producing a variety of light sources for illuminating a workpiece. See for example U.S. Pat. No. 4,893,223 and No. 5,038,258. More recently U.S. Pat. No. 5,690,417, which is owned by the assignee of the present application, discloses the use of LED's in surface illuminators along with an associated Fresnel lens for redirecting light from LED lamps toward a workpiece that is to be inspected. In that patent, the LED's are arrayed in coaxially disposed, radially spaced arrays with the light emitting ends of the LED's disposed in a common plane, and with a light beams emitted thereby being directed along spaced, parallel axes. The associated Fresnel lens redirects the beams angularly towards a workpiece. Such an apparatus is capable of providing illumination at angles of incidence at a range having a maximum of approximately 45.degree..
It is an object of this invention, therefore, to provide an improved surface illuminator which utilizes LED lamps for providing illumination, but which also has the capability of providing illumination at higher angles of incidence then was heretofore possible.
Still another object of this invention is to provide an improved surface illuminator which utilizes LED lamps and associated, flexible circuit boards which enable the lamps to be arrayed selectively in cylindrical or conical arrays.
A more specific object of this invention is to provide an improved LED illuminator of the type described, which employs in combination with the LED light sources, modified or hybrid Fresnel-type diffusers which enable light beams to be refracted and directed onto a workpiece at angles of incidence ranging between 15.degree. to 80.degree..
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.